Treatment of sticklac to obtain therefrom seedlac



Patented Mar. 17, 1953 UNITED STATES PATENT OFFICE TREATMENT OF STICKLAC TO OBTAIN THEREFROM SEEDLAC Robert Hutchison Turnbull, Calcutta, India No Drawing. Application December 14, 1951, Se-

rial No. 261,758. In India July 26, 1950 11 Claims.

The invention is for improvements in and relating to the treatment of sticklac whereby to obtain therefrom seedlac. The invention has for a particular object so to treat the poorer qualities of sticklac, such as those known to the trade as Siam sticklac, as to obtain therefrom good quality seedlac equivalent, for example, to that known in the trade as Kusmi seedlac.

Sticklac (i. e. the original form in which the lac is gathered) contains the lac deposits mixed with sticks or twigs from which it derives its name and also foreign matter such as dirt, dust, sand, albumen, nitrogen and a relatively high quantity of colouring matter which is more particularly a red dye. Seedlac is the material obtained after refining or purifying the raw sticklac, the treatment having for object to remove the sticks, twigs, dirt and other impurities and as much as possible of the colouring matter, so as to obtain a product which will require as low a bleach consumption as possible in order to obtain a commercially useful product. Qualities of seedlac used for commercial purposes are generally determined and classified by their nitrogen and bleach numbers and content of impurities.

It is already known to treat sticklac to produce seedlac by various processes having for object the removal of the impurities and colouring matter aforesaid, the steps involved comprising a preliminary grinding and washing of the sticklac, the treatment of the ground and washed material with one or more chemicals to remove the colouring matter, and a further washing and drying.

The present invention provides an improved process whereby the impurities and colouring matter are more efficiently removed than hitherto and there is obtained a seedlac which has a lower nitrogen content, a lower content of impurities and an improved bleach consumption and rate of bleach as compared to seedlac hitherto obtained from similar quality sticklac.

The process of the invention is based primarily on the step in the treatment of sticklac to obtain seedlac, which consists in subjecting the said sticklac to the action of ammonium sulphate for the purpose of removing colouring matter, albuminous matter and other foreign matter from the lac grains.

In particular and preferably, the process of treatment according to the invention comprises the successive steps of grinding and washing the sticklac, subjecting the same to the action of ammonium sulphate as aforesaid and thereafter following the said ammonium sulphate treatment with conventional or special washing and/ or other treatments to recover the refined lac grains.

The advantageous results obtained in the separation of foreign matter from the lac grains by the use of ammonium sulphate in the method of the invention are believed to be due to the faculty of ammonium sulphate to promote its adsorption by the sticklac. It has been found that ammonium sulphate is readily dissociated and, when used in the method of the invention, the whole ionic system is so disturbed that all foreign matter is readily released from contact with the sticklac and so separates out from the system by alteration of surface tension and is precipitated.

The ammonium sulphate treatment according to the invention is effected with the ammonium sulphate in the form of an aqueous solution and the complete process steps comprise grinding and washing the sticklac with water, recovering the ground and washed lac material, subjecting the same in a ball mill or the equivalent to the action of a solution of ammonium sulphate, separating the treated lac from the solution containing the impurities removed from the lac grains, repeating the milling operation one or more times, recovering the treated lac, subjecting the same to one or more washings, with a solution of common salt, further washing the treated lac with water, and drying the final product.

Preferably, the grinding treatment in the ball mill is effected with at least a 0.5% solution of ammonium sulphate over a period of about four to five hours and the millings are repeated until the wash water shows no further signs of colouring matter. For the washing with common salt, a solution of about 1.2 specific gravity is preferably used and, after stirring, settling is effected whereby the dirt and the impurities fall to the bottom and the lac floats to the top of the solution. The clean lac is then separated from the liquid residue and further washing with common salt solution is repeated one or more times. The washed lac is then subjected to a combined centrifugal and filter action while being further washed with water, whereafter it is dried in the centrifugal machine, followed by air drying.

In order that the invention may be more fully understood, a detailed example thereof will now be given in the following by way of illustration.

ExampZe.-Siam sticklac is roughly ground in a disintegrator to pass through a 10 mesh sieve, or coarser. The ground material is then sieved on an mesh sieve so as to get rid of the fine dust of foreign character and the sand. Before grind- 3 ing roughly, any bare sticks or twigs are first removed by hand.

The sticklac so ground is placed in an open receptacle, such as a tub, and thoroughly washed '4 before all the foreign matter is removed from the sticklac. The salt solution is then recovered by passing the same through a filter press and used again for washing purposes. This is easily observed when no further precipitation of im- With water, by mixing with a beater, such as a 5 wooden stick. This removes a quantity of the purities is seen.

red colouring matter or dye. After mixing thor- The washed sticklac is then transferred to a oughly, the 'sticklac is allowed to settle and the cen rifugal with perforated "sides, over which a Wash water is removed by syphonihg, passing the good filter cloth is placed. Then, when the censyphoned water through an 80 mesh sieve to catch trifugal is running, the seedlac is washed with any particles of sticklac. This washing is con water until the wash water is free from chlorides, tinued until all the red dye is removed by the as ascertained by chemical test. As soon as such water which generally takes about three "or four result is achieved, the sticklac is dried by means washings, depending on the nature of thes'tickor a "centrifugal machine and finally air dried in lac. perforated shelves, covered with gunny.

The washed sticklac is then transferred to an In carrying the above-described process of the 80 mesh sieve to enable the water to be drained invention intofprac'tiee, a horizontally-driven cenofi. The sticklac is then collected and "pieces 'trifugal machine is preferably employed, which in a porcelain ball mill, one third of which is enables the sticklac under treatment to be con already filled with porcelain balls of about one tinuously fed and washed in one operation. inch in diameter.- Aquanti-ty of 9.5% ammonium By way of example, it is indicated that the sulphate solution is added to fill the ball rnil'l average impurities content of sticklac treated by up toabout two thirds -of its capacity. In some the method of the invention and as determined instances, the use of about 1.6% ammonium :sulby standard methyl or ethyl alcohol tests is found phate-sol-ution may be -required, depending upon 1:, to be between about Q.36% and 1.120%, which is the quality of the stick-lac. The ball-mill is then considerably lower than the impurities content rotated at a;speed of about to 5D revolutions obtained with previously known methods of treatper -m-inute for a .peziod of about 'four to five ment. Further, on six samples oi poor quality hours. 7 After -sueh ;milling, the ball mill is --re Siam Sticklac 33, E Emil F treated by' moved fromits carriage and the sticklac allowed 3 process according to the invention, the following to settle. The coloured (red) water is then reresults were ebtained in respect of nitrogen conmoved by syphoni'ng andpassed through an 80 tent and bleach tests.

1 H .crcs- "ooioumrma'chstl. Samples j f oi' b' & with i ii tl i nfi a d grams of lac 3:247 grs 0.06 65 More "yellow th'ail' Coll'sidera'bl'y slower.

standard, and also 7 than C.

O=275 g'rs 0.05 '55 Somewhatmorey'cl- 'Considerably slower low than standard I butless so than B. and-also than E.

,D*= 250 rs '60 Similar to '0 Similar'to o.

r is's'gis "60 'sn iiar'to B Similar to B.

FineKusmistandard mesh *sieveto collect any escaping sticklac. The process is then repeated with three'or four millings until the wash water shows no further signs of red colour.

When this stage is reached, the sticklac is removed to a 'separ'atona preferred formof which has "a rectangular open top, with square sides, which sits on a foundation 0f four sloping sides and which is provided with two glass windows, one on either side, for viewing the operation' of washing. At the base is fixed a tube witha valve for drawing off the washwater. To the stickla 'c, now in the separator, is added a quantityof common salt solution of 1.2 specific gravity. The whole is well mixed with a beater, such "as 'a wooden stick, and then allowed to settle until the salt solution becomes -"clear. At this stage, all the foreign matter, such as dirt and foreign organic matter, as well as-most of the albuminous matter, falls to the bottom, while the sticklac goes to the top of theliquid. The wholeof the salt solution is then drawn off, along with the residues which'are at the bottom of the-separator, leaving the clean sticklac in the separator. A

further quantity of the same strength of *salt solution is then added to the separator, and the same Washing prqcessrepeated. lf-hree or four washings *w'ithsalt solution may be necessary The bleach tests were carried out employing as standard a sample of fine vKusrni standard 1937. The directions followed were those usual for-standard Kusmi seedlac'for all samples except sample A where, owing to the low bleach consumption, the method adopted waste add 25 cos. of bleach solution to a total volume of 275 ccs., so that the 240 cc. aliquot taken next day corresponded to 2G cc.-of bleach solution and-30 grams of seedlac. The colour of 'all samples after bleaching wasfound generally to be a pale yel lowish-eream.

*It will be seen that lay-means of the invention it is possible to treat poor quality sticklac "to obtain therefrom a quality of seedlac which is comparable with, or even superior to, fine Kusmi standard seedlac in respect of nitrogen and impurities-content and bleaohconsumption. It will be understood, however, that the invention is not limited to the specific details thereof which have been given above by way of example and that many modifications of the same may be made within the scope of theappended claims.

1. -In the treatment of stieklacto produceseedlac, the improvement which comprises the step of subjecting the :sticklac to theaction of ammonium sulphate :inaqueous solution to cause separation of colouring matter, albuminou matter and other foreign matter from the lac grains.

2. In the treatment of sticklac to produce seedlac, the improvement which comprises the steps of subjecting the sticklac to the action of an aqueous solution of ammonium sulphate to cause colouring matter, albuminous matter and other foreign matter to separate from the lac grains and washing with an aqueous solution of common salt.

3. A process for the treatment of sticklac to produce seedlac, which comprises grindin and washing the sticklac, subjecting the ground and washed sticklac to the action of ammonium sulphate in aqueous dilute solution to cause colouring matter, albuminous matter and other foreign matter to separate from the lac grains, removing the separated matter, and washing and drying the resultant treated lac.

4. A process for the treatment of sticklac to produce seedlac, which comprises grinding and washing the sticklac with Water, recovering the ground and washed lac material, milling said lac material in admixture with an aqueous dilute solution of ammonium sulphate, recovering the sotreated lac material from said mixture after milling, washing said lac material with a solution of common salt, and then washing with water and drying.

5. In the treatment of sticklac to produce seedlac, the improvement which comprises the step of subjecting the sticklac to the action of ammonium sulphate in the form of an at least 0.5% aqueous solution to cause colouring matter, albuminous matter and other foreign matter to separate from the lac rains.

6. In the treatment of sticklac to produce seedlac, the improvement which comprises the step of subjecting the sticklac to the action of ammonium sulphate in the form of an at least 0.5% aqueous solution over a period of about four to five hours, to cause colouring matter, albuminous matter and other foreign matter to separate from the lac grains.

'7. A process for the treatment of sticklac to produce seedlac, which comprise grinding and washing the sticklac with water, recovering the ground and Washed lac material, milling said lac material in admixture with an at least 0.5 aqueous solution of ammonium sulphate over a period of about four to five hours, recovering the sotreated lac material from said mixture after milling, washing said lac material with a solution of common salt, and then washing the treated lac with water and drying the final product.

8. In the treatment of sticklac to produce seedlac, the improvement which comprises the steps of subjecting the sticklac to the action of ammonium sulphate in the form of an at least 0.5% aqueous solution over a period of about four to five hours, to cause colouring matter, albuminous matter and other foreign matter to separate from the lac grains, and washing the treated lac with a common salt solution of about 1.2 specific gravity.

9. A process for the treatment of sticklac to produce seedlac, which comprises grinding and washing the sticklac, subjecting the ground and washed sticklac to the action of an aqueous dilute solution of ammonium sulphate to cause colouring matter, albuminous matter and other foreign matter to separate from the lac grains, removing the separated matter and washing the treated lac with a common salt solution of about 1.2 specific gravity and drying the resultant treated lac.

10. In the treatment of sticklac to produce seedlac, the improvement which includes the steps of subjecting the sticklac to the action of an aqueous dilute solution of ammonium sulphate to cause colouring matter, albuminous matter and other foreign matter to separate from the lac grains, washing the treated lac with a common salt solution, and subjecting the treated lac to a combined centrifugal and filter action while being washed with water, whereafter it is dried by centrifuging, followed by air drying.

11. A process for the treatment of sticklac to produce seedlac, which comprises grinding and washing the sticklac with water, recovering the ground and washed lac material, milling said lac material in admixture with an at least 0.5% aqueous solution of ammonium sulphate over a period of about four to five hours, recovering the so-treated lac material from said mixture after milling, washing said lac material With a solution of common salt of about 1.2 specific gravity, and finally subjecting the treated lac to a combined centrifugal and filter action while being washed with water, whereafter it is dried by centrifuging, followed by air drying.

ROBERT HUTCHISON TURNBULL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1544,4191 Rawolle Oct. 4, 1927 FOREIGN PATENTS Number Country Date 103,006 Great Britain Feb. 14, 1917 188,296 Great Britain May 7, 1923 

1. IN THE TREATMENT OF STICKLAC TO PRODUCE SEEDLAC, THE IMPROVEMENT WHICH COMPRISES THE STEP OF SUBJECTING THE STICKLE TO THE ACTION OF AMMONIUM SULPHATE IN AQUEOUS SOLUTION TO CAUSE SEPARATION OF COLOURING MATTER, ALBUMINOUS MATTER AND OTHER FOREIGN MATTER FROM THE LAC GRAINS. 